Problems With Boxwood Hedges

Boxwood hedges can be trimmed into formal shapes.

Common boxwood (Buxus sempervirens) has been cultivated in the U.S. since Colonial times. Boxwoods can be an effective choice when planting a new hedge, whether you choose to trim your plants into a formal shape or allow them to grow more freely, creating a softer and more free-form hedge. Depending on the variety you choose, boxwoods are suitable for U.S. Department of Agriculture plant hardiness zones 4 through 9.

Effects of Weather

Boxwoods prefer a partially shaded site where they receive full sun for only part of each day and are not subject to strong wind. Full-time exposure to hot sun, especially in the presence of wind, can cause unattractive, brown edges on boxwood leaves. In areas where frost occurs during winter, cold winds can produce more extensive damage to a boxwood hedge, causing bronzing of foliage and dieback of some branches, especially in the center of the hedge. You can lessen the likelihood of damage by spraying your plants with an anti-desiccant compound during the fall, before harsh weather arrives.

Insect Problems

Several insects can be especially destructive for a boxwood hedge. Named for their preference for these plants, they include the boxwood leafminer, boxwood mite and boxwood psyllid. The leafminer is the most serious of the three, causing leaves to turn brown and eventually drop from the plants. Boxwood mites cause yellow stippling of leaves, giving the plant an unhealthy, gray-leaved appearance. The adult psyllid is a small, green insect with clear wings that resembles a tiny cicada. Both immature and adult psyllids feed on leaves, causing them to become cup-shaped and stunting the plant's growth. Control these pests with insecticidal sprays for use in the home garden and labeled effective against boxwood pests.

Twig Blight

Twig blight is a disease of boxwoods that is also called decline or dieback. It causes plants to appear weak or spindly, with dead branches appearing sporadically. Sometimes older leaves begin to drop, while the younger foliage turns yellow. According to the Clemson Cooperative Extension, the cause of twig blight is complex, involving several fungi, nematodes in soil, and possibly poor cultural practices. If the problem develops in your hedge, Clemson recommends a soil analysis for pH, nutrient availability and nematodes. Thinning plants to maintain good air circulation, pruning dead or dying branches back to healthy tissue and renewing underlying mulch yearly should help prevent problems with twig blight.

Root Rot and Canker

Fungal micro-organisms cause root rot and canker, two potential diseases in boxwoods. In root rot, leaves turn light green and the plant declines, with bark rotting and peeling from branches in the crown of the plant. Canker develops when the fungus Volutella buxi infects boxwoods, causing slow growth in spring. Leaves eventually become tan and turn upward, rather than spreading out from stems. Bark may become loose and peel, showing gray or blackened wood underneath. Both diseases are caused by poorly drained soil that is constantly warm and wet. Application of fungicide to the soil can help prevent these problems, as does quick removal of dropped leaves and dying branches.

About the Author

Joanne Marie began writing professionally in 1981. Her work has appeared in health, medical and scientific publications such as Endocrinology and Journal of Cell Biology. She has also published in hobbyist offerings such as The Hobstarand The Bagpiper. Marie is a certified master gardener and has a Ph.D. in anatomy from Temple University School of Medicine.